The edit blog form is currently accessed via /network/sites.php?action=editblog&id=1. Accessing the form via sites.php confuses screen options and other UI elements. The form should be accessed via edit.php instead. In general, the blog edit code in the network admin needs a refactor.

Move edit.php to site.php

Access the blog edit form via site.php?action=edit

Put the form in edit-blog-form.php

Use proper meta boxes and screen options for the form, using edit-form-advanced.php as inspiration